Development and characterisation of SiAlON composites with TiB2, TiN, TiC and TiCN

30 vol% of TiB₂, TiCN, TiN or TiC was added to a sialon matrix with an X-phase sialon (Si₁₂Al₁₈O₃₉N₈) and an Al₂O₃–Si₃N₄ (77/23 wt%) starting powder composition and hot pressed at 1650°C in vacuum. The microstructures of the obtained composites were characterised by means of X-ray diffraction and electron microscopy, and the mechanical properties; E-modulus, hardness, bending strength and fracture toughness were measured and evaluated.Fully dense composites with an X-phase sialon or a polyphase Al₂O₃–-sialon–X-sialon matrix with 30 vol% of TiB₂, TiN and TiCN were obtained. TiC, added as a dispersed phase, however reacts with the nitrogen from the Si₃N₄ during liquid phase sintering, with the formation of TiC_1–x N _x , SiC and a changed sialon matrix composition. In the case of the X-phase sialon starting composition, a mullite matrix is obtained after sintering. The microstructural observations with respect to the sialon-TiC composites are found to be in agreement with the thermodynamic calculations.